Could you change an automatic to a manual? Would a 5 speed bolt up just like the automatic? And one more thing automatics are emissions exempt in california but are manuals? Are they exempt forever or just a period of time?
Most anything automotive can be done these days. A better question to ask is _would_ you pay for the conversion :?: No I don't have a price in mind but I'd bet it would exceed $2,000 and quite possible 3,000 with _used_ parts. DIY, probably 1/2 that.
As far as emissions you'll have to wait for a CA member in the know to reply. But forever is a long time.
The "lean burn" that allows hyper MPG when driven for such is a slightly different engine than supplied with the CVT. Different PCM too :!:
So a CVT's engine coupled with a 5 speed tranny won't have the same MPG potential as a factory equipped combination. And if your thinking is "reversed" emissions will likely be higher with just the tranny swap too.